Characterization of the known Mycoplasmas by biochemical and physiological properties, DNA base composition, and nucleic acid homology will be continued to determine the extent of the fundamental heterogeneity that cleaves the group, and to delineate subgroups of similar mycoplasmas. A relationship uncovered between mycoplasmas and streptococci will be examined to determine whether similarities between these organisms is coincidental or due to a true relationship. Another study area will be leukocyte response to pathogenic mycoplasmas and their cell fractions.